HISTORY: 21 year old female, D-1 gymnast, with 2 weeks of tight and achy right triceps pain. Athlete noted pain after practice, denies specific injury. Her pain is worse with resisted elbow extension. She is treating conservatively, rehabbing with ATC with strengthening both shoulder and arm, and is now tolerating forward tumbling, but soreness remains with backward tumbling. She feels she has plateaued in progress. PE: Grossly unremarkable, no ecchymosis or swelling. She has tenderness to triceps muscle belly without palpable muscle defect. ROM and strength are intact at her shoulder and elbow. She is neurologically intact distally. DDX:Triceps tear, triceps tendinopathy, shoulder pathology TEST & RESULTS: MSK US-proximal, mid belly of long head of triceps muscle fiber disruption with 2 cm fiber gap and hematoma. Extensive hyperemia in zone of injury and 8 cm of fascial thickening. Active contraction demonstrates fiber gap without contraction at zone of injury and abnormal contraction of surrounding fibers. FINAL/WORKING DX: Acute tear of right triceps, long head, grade 2b TREATMENT & OUTCOMES: Platelet-rich plasma injection into triceps tear followed by compression and 2 days rest. Progressive, sport-specific, pain-free strengthening with ATC guidance. Athlete avoided weight bearing on hands and stretching of triceps. She tolerated dance and trampoline work without issue. Upon reaching 80% speed/power without pain or functional limitation, 2 weeks after diagnosis, we performed serial US exams to evaluate tissue healing and guide progressive muscle loading. 2 week US demonstrated decreased fascial thickening, 2 cm fiber gap w/hyperemia persisted. Absent contraction at site of injury remained, abnormal contraction of surrounding fibers was improved. Continued rehab, did not progress beyond 80% at this time regardless of pain-free status. 4 week US revealed resolution of hematoma and fascial edema. Mild hyperemia remained at zone of injury. Some abnormal contraction at site of injury present, and normalized contraction of surrounding fibers. Athlete was released to gradually RTP under ATC guidance. Athlete progressed overhead loading, reached 100% power/speed and was advanced to forward and eventually backward tumbling. She tolerated full RTP 8 weeks after initial US. Athlete remains without re-injury.